A C-D(carbon–deuterium) bond is electronically much like a

QUESTION:

A \(\mathrm{C}-\mathrm{D}\) (carbon-deuterium) bond is electronically much like a \(\mathrm{C}-\mathrm{H}\) bond, and it has a similar stiffness, measured by the spring constant, . The deuterium atom has twice the mass  of a hydrogen atom, however.

(a) The infrared absorption frequency is approximately proportional to \(\sqrt{k / m}\), when one of the bonded atoms is much heavier than the other, and  is the lighter of the two atoms (H or D in this case). Use this relationship to calculate the IR absorption frequency of a typical \(\mathrm{C}-\mathrm{D}\) bond. Use \(3000 \mathrm{~cm}^{-1}\) as a typical \(\mathrm{C}-\mathrm{H}\) absorption frequency.

(b) A chemist dissolves a sample in deuterochloroform \(\left(\mathrm{CDCl}_{3}\right)\), then decides to take the IR spectrum and simply evaporates most of the \(\mathrm{CDCl}_{3}\). What functional group will appear to be present in this IR spectrum as a result of the \(\mathrm{CDCl}_{3}\) impurity?

Equation Transcription:

Text Transcription:

C-D

C-H

k/m

C-D

3000 cm^{-1}

C-H

(CDCl_{3})

CDCl_{3}

CDCl_{3}